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Inter- and intraspecific parasitism Dik Heg The major types of organism-organism interactions 1. Competition Interspecific competition (competition between different species) Intraspecific competition (competition within the same species) 2. Predation Interspecific predation (predator-prey interactions) Intraspecific predation (cannibalism, infanticide) 3. Cooperation Interspecific cooperation (mutualism, symbiosis) Intraspecific cooperation (kin selection, reciprocal altruism) 4. Parasitism Interspecific parasitism (host-parasite interactions, e.g. ectoparasites, endoparasites, viruses, pathogens) Intraspecific parasitism (within-species brood parasitism, e.g. egg dumping, sneaking) Interspecific parasitism: definition Parasite (pathogen) = organism that obtains its nutrients from one or a very few host individuals, causing harm* but not causing host death immediately. Parasitoid = egg to larval organism that obtains its nutrients from a single host individual, causing host death in the end (incl. parasitic Hymenoptera and Diptera insects). ´Host´ Cost No cost, no benefit Benefit Co-species (always benefit) parasite commensalist mutualist or symbiont Interaction Parasitism Commensalism Mutualism or Symbiosis Parasitism O Commensalism Mutualism or Symbiosis Cost and benefits in terms of fitness: life expectancy (age) * reproductive success/age step * harm = fitness of host is reduced, though perhaps only in appropriate circumstances (e.g. a sufficient number of parasites or when the host is in poor body condition) Interspecific parasitism 1. Example of the effect of a parasite on survival, growth and fecundity of a host Interspecific parasitism 2. The diversity of interspecific parasites Microparasites = multiply directly within their host (usually within the host cells): bacteria, viruses, protozoa, fungi. Trypanosoma brucei (sleeping sickness, Schlafkrankheit) Parasitic mite Hydraphantes tenuabilis Water bug Hydrometra myrae Macroparasites = grow in their host, but multiply by producing infective stages which are released from the host to infect new hosts (or intermediate hosts). cestode worms Schistocephalus solidus in stickleback Brood parasites = use resources of the host (e.g. food, shelter), and/or they feed on larvae or eggs. Often mimicry involved (e.g. chemical, tactile, morphological). Special case: slave-making ants. Interspecific parasitism 3. Interspecific parasitism 4. 1 in liver The malaria cycle Microparasites: 1. Directly transmitted from host to host: a. immediate transfer: e.g. venereal diseases, influenza, measles b. dormant period: e.g. amoebic dysentry, plant pathogen spores in soil in blood Entamoeba histolytica trophozoites (amoebic dysentry, Amüben-Ruhr) 2. Indirectly transmitted via some other species (vector or intermediate host(s)) Vector: anopheline mosquito Plasmodium falciparum (malaria) in mosquito within red blood cells Interspecific parasitism 5. Macroparasites: platyhelminth worms (tapeworms, trematodes) acanthocephalans (intestinal) nematodes lice, fleas, ticks, mites, fungi 1. Directly transmitted from host to host 2. Indirectly transmitted via some other species (vector or intermediate host(s)) Plasmodium vivax, after Vickerman & Cox 1967 Interspecific brood parasites Dactylogyridae worm of fish Brood parasites = use resources of the host (e.g. food, shelter), and/or they feed on larvae or eggs. Many examples in insects, but also some examples in birds and fish. Most important taxon: Hymenoptera, e.g. parasitoid wasps Cleptoparasite = idem, only uses resources. Example: Parastizopus armaticeps with cleptoparasite Eremostibes opacus (tenebrionid beetles from the Kalahari desert) Interspecific parasitism 7. Interspecific parasitism 4. Example brood parasites: Atemeles pubicollis Staphylinid beetle Atemeles pubicollis enters colony of Formica rufa Interspecific parasitism 6. Beetle larvae produce glandular secretion which induces grooming. Larva begs to obtain regurgated food Example brood parasites: ant parasites Limulodid beetle Paralimulodes wasmanni on Neivamyrmex nigriscens Mite Circocylliba sp. on Eciton sp. Mite Antennequesoma sp.on army ant Interspecific parasitism 9. Nicoletiid silverfish Trichatelura manni on Eciton sp. Mite Macrocheles rettenmeyeri on Eciton dulcius Histerid beetle Euxenister caroli on Eciton burchelli Interspecific parasitism 10. 2 Example brood parasites: slave-making ants Slave-maker ant Epimyrma stumperi enters nest and strangles, kills.... .... Host queen ant Leptothorax tuberum Population dynamics of directly transmitted microparasites Basic reproductive rate: R0 = Σ lx * mx lx = proportion of individuals surviving until age x mx = average number of offspring produced per individual at age x Example Phlox drummondii: R0 = 2.41 This slave-maker ant Formica subintegra has a large Dufour´s gland for the production of ´propaganda substances´ that will scatter the slaveants (also from the genus Formica) during raids. For parasites usually Rp is used: It is contrasted with the Dufour´s gland of F. subserica, which is an ordinary ant. Rp = 1: the transmission threshold Rp < 1: disease will die out Rp > 1: disease will spread Rp = average number of new cases of the disease that arise from each infected host Interspecific parasitism 11. Directly transmitted microparasites: determinants of Rp Interspecific parasitism 12. Directly transmitted microparasites: determinants of Rp Rp = average number of new cases of the disease that arise from each infected host Rp = average number of new cases of the disease that arise from each infected host Rp = β * N * ƒ * L Rp = β * N * ƒ * L Where: β = transmission rate of the disease = frequency of host contact * probability that host contact leads to infection (0.0 – 1.0) Proportion of alive infectious hosts * time alive Number of new hosts getting infected N = density of (susceptible) hosts (0.0 - ∞) ƒ = fraction of hosts that survive long enough to become infectious themselves (0.0 – 1.0) L = average period of time over which the infected host remains infectious (>0 - ∞) Note: in most biotrophic parasites L is the period of the host`s life when it is infectious, but for necrotrophic parasites and some biotrophs, the parasite may remain infectious long after the host has died (and decomposed) Interspecific parasitism 13. Directly transmitted microparasites: determinants of Rp Interspecific parasitism 14. Vector-transmitted microparasites: determinants of Rp Rp = 1: transmission threshold ⇒ Nt = 1 β*ƒ*L : density threshold Both the life cycle of the host h and the vector v has to be taken into account: So if parasites (diseases) are highly infectious (large β), or are unlikely to kill their host (large ƒ), or give rise to long periods of infectiousness (large L), they will have high Rp values and can persist in small populations (Nt is small). Rp = β2 * Nv * ƒv*ƒh * Lv*Lh Nh Note: β is squared, because when the vector bites, it both can get infected by the host itself, or pass the infection to a new host when it is already infected itself. Hosts acquiring immunity against parasite versus mutant parasites arising or influx of new hosts => cycles of parasite incidence. Interspecific parasitism 15. Interspecific parasitism 16. 3 Vector-transmitted microparasites: determinants of Rp For macroparasites it is possible to determine the reproductive success and life expectancy of a single individual parasite = the sum of offspring produced that themselves survive to produce offspring. Rp = average number of new cases of the disease that arise from each infected host Rp = 1: transmission threshold ⇒ Nv = Nh 1 β2 * ƒv * ƒh * Lv * Lh Directly transmitted macroparasites: determinants of Rp : the ratio-of-densities threshold Rp = (λ*ƒa*La) * (β*N*ƒi*Li ) Hence, disease control measures are usually aimed directly at reducing the numbers of vectors, and only indirectly at the parasite. This reduces the likelihood that the final host (e.g. man) will get infected, so less direct treatments of the parasite in the final host are necessary. Reproductive contribution of: Interspecific parasitism 17. adult infective stage λ = rate of egg production per adult parasite ƒa = proportion of parasites in the host that attain sexual maturity La = expected life span of adult parasite β = transmission rate N = host density ƒi = proportion of the parasite transmission stage that become infective Li = expected life span of the infective stage outside the host Interspecific parasitism 18. Density-dependence within the host is crucially important for the reproductive rate of macroparasites Parasitoids Parasitoid = egg to larval organism that obtains its nutrients from a single host individual, causing host death in the end (incl. parasitic Hymenoptera and Diptera insects). λ = rate of egg production per adult parasite ƒa = proportion of parasites in the host that attain sexual maturity La = expected life span of adult parasite extremely numerous group of organisms, since an estimated 25% of the world species are parasitoids (since most insect species host at least one parasitoid, and some parasitoids host parasitoids themselves = superparasitism by same parasite species, or hyperparasitism by other parasite species) Interspecific parasitism 19. Parasitoids hyperparasitism web Interspecific parasitism 20. Effects of parasites on behavioural ecology: case study barn swallow ♀ ♂ Interspecific parasitism 21. ♂ ♀ Interspecific parasitism 22. 4 Effect of barn swallow parasites on fitness Barn swallow parasites Interspecific parasitism 23. Interspecific parasitism 24. Effect of barn swallow parasites on fitness Brood parasitism Fish: 2-3 species Birds: ~1% of all species (50% of the cuckoos, two genera of finches, five cowbirds, and a duck) Interspecific parasitism 25. Catfish Synodontis multipunctatus Brood parasitism by catfish Synodontis multipunctatus Number of broods examined: Simochromis babaulti & S. diagramma Pseudosimochromis curvifrons Tropheus moorii Mouthbrooding cichlids % with catfish Brood parasitism by catfish from Lake Tanganyika: Interspecific parasitism 26. Host´s eggs and offspring are consumed by the catfish offspring.... Gnathochromis pfefferi Ctenochromis horei Interspecific parasitism 27. Interspecific parasitism 28. 5 Brood parasitism by birds: cuckoo Cuculus canorus References: N.B. Davies and others (1987-2003) M. & B.Taborsky et al. Interspecific parasitism 29. Cuckoo Cuculus canorus Cuckoo Cuculus canorus: mimicry of host eggs host cuckoo model Robin (Erithacus rubercula) Pied wagtail (Motacilla alba) (Prunella modularis) Dunnock Individual females specialize on specific host species, e.g. Reed warbler Acrocephalus scirpaceus Meadow pipit Anthus pratensis Dunnock Prunella modularis (Acrocephalus scripaceus) Reed warbler (Anthus pratensis) Meadow pipit Great reed warbler (Acrocephalus arundinaceus) Gibbs et al. 2000. Nature Interspecific parasitism 31. Cuckoo Cuculus canorus Cuckoo Cuculus canorus 1985-86 1985-86 Hosts-parasite co-evolution 1. 1997 1997 0 week 10 6 Cuckoo Cuculus canorus Cuckoo Cuculus canorus Hosts-parasite co-evolution 2 (Lotem et al. 1995. Animal Behaviour 49: 1185-1209). Hosts-parasite co-evolution 3. Host strategy Probability of event Accept p parasitized 1-p non-parasitized The payoff of an accepter will be equal to that of a rejecter when: p parasitized Reject 1-p non-parasitized Payoff to host 0 X 1-e rejects cuckoo e rejects own offspring* 1-e no error e rejects own offspring** X – 1*** 0 X X-1 X = number of host offspring * = mistakingly rejects own offspring instead of cuckoo offspring! ** = mistakingly rejects own offspring, despite there is no cuckoo in the nest!! *** = if the host kills own offspring by removing the parasite (e.g. breaks own eggs), term will be X – 2 .. Intraspecific parasitism: definition Conspecific individual using the brood care of other individuals, without providing brood care themselves. Females: egg dumping. Males: extra-pair fertilizations, sneaker spawning. (1-p)X = p(1-e)(X+1) + (1-p)(1-e)X + (1-p)e(X+1) ⇒ Rejection error e = (p-pX) (2p-pX-1) Natural parasitism level p is ~3%, so low rejection error level of ~7-8% would make payoff accepter = rejecter! Interspecific parasitism 36. Intraspecific parasitism: sperm competition Females: egg dumping virtually equivalent with interspecific brood parasitism. Males: sperm competition plays an important role in the relative success of extra-pair copulations or sneaker spawnings. Sperm competition = the likelihood that sperm of a particular male will fertilise the ova, depending on the sperm of other male(s) in the reproductive tract of the female Intraspecific parasitism 1. Intraspecific parasitism 1. 7